I don't disagee with you as to how their rules are written. But perhaps "may contain a 10% possibility of occuring" shouldn't have been left out of the text.
It just has never happened to me, ergo my value perception.
3 days ago on UA129 I was
#2 then bumped to
#3 with 7 seats open, and didn't get upgraded until I was at the gate on a paid upgrade (miles + $). Happens way too much IMHO.
FWIW they offer you a buy up to Plat at year end for $1400 USD. No thanks.